Utilisation de l'isoflurane en circuit fermé Avantages économiques

Abstract

The present study was designed to assess whether isoflurane requirement was significantly affected by fresh gas flow in a closed-circuit system. Sixty patients scheduled for orthopaedic procedures were randomly assigned into three groups. In group A (n=20), anaesthesia was conducted with a fresh gas flow of 482.5±186.6 ml · min −1, corresponding to the patient's metabolic demand. In group B (n=20), the fresh gas flow was 2000 ml · min −1. In group C (n=20), it was adjusted to the ventilation minute, i.e. 7145±986 ml · min −1. Artificial ventilation was conducted using a tidal volume of 10 ml · kg −1 and a rate of 10 to 12 c · min −1. Anaesthesia was induced after 10 min denitrogenation with fentanyl (4 μg · kg −1), thiopentone (4 mg · kg −1) and vecuronium (0.1 mg · kg −1). Fio 2 was then brought to 0.5 in nitrous oxide and was monitored continuously using a polarographic oxymeter. Liquid isoflurane was injected in the expiratory limb of the circuit using an electrical syringe driver. Alveolar concentration of isoflurane was set at 0.92 vol. % according to Lowe and Ernst [5]. Statistical analysis was carried out using Student's test for means. Anaesthesia lasted 138±88.3 min in group A, 125.5±45.1 min in group B and 146.5±50 min in group C, no difference being significant. The requirements in liquid isoflurane for the first hour were 5.85±1.32 ml in group A, 10.75±1.12 ml in group B and 67.15±19.51 ml in group C. The total isoflurane consumption reached 11.32±6.73 ml in group A, 19.20±7.12 ml in group B and 157.20±40.41 ml in group C. The cost of isoflurane during the first hour (in US dollars; 1 U$ = 6,14 FF) was 4.30±0.97 in group A, 7.79±0.93 in group B and 49.32±14.33 in group C. The total cost reached 8.28±4.94 in group A, 14.10±5.23 in group B and 115.47±29.68 in group C. The difference in consumption and expense between groups A, B and C were significant (p<0.001). As isoflurane is 4.4 times more expensive than enflurane and 9.7 more than halothane, the dramatic saving with closed-circuit anaesthesia led to save a large sum of money, thus compensating the expenses for gas and vapour analysers which increase the security of low flow anaesthesia.